An Extended Visual Cryptography Algorithm for General Access Structures
ABSTRACT Conventional visual secret sharing schemes generate noise-like random pixels on shares to hide secret images. It suffers a management problem, because of which dealers cannot visually identify each share. This problem is solved by the extended visual cryptography scheme (EVCS), which adds a meaningful cover image in each share. However, the previous approaches involving the EVCS for general access structures suffer from a pixel expansion problem. In addition, the visual cryptography (VC)-based approach needs a sophisticated codebook design for various schemes. In this paper, we propose a general approach to solve the above-mentioned problems; the approach can be used for binary secret images in noncomputer-aided decryption environments. The proposed approach consists of two phases. In the first phase, based on a given access structure, we construct meaningless shares using an optimization technique and the construction for conventional VC schemes. In the second phase, cover images are added in each share directly by a stamping algorithm. The experimental results indicate that a solution to the pixel expansion problem of the EVCS for GASs is achieved. Moreover, the display quality of the recovered image is very close to that obtained using conventional VC schemes.
Conference Paper: A (m, m)VCS with consistent size reconstruction using full binary tree[Show abstract] [Hide abstract]
ABSTRACT: Visual cryptography method of secret sharing suffers from pixel expansion and low contrast. Such kind of problem persist in approximately all previous existing visual cryptographic algorithm whereas there are few visual cryptographic method which tries to improve but not done with whole similarity. In this proposed method, we have designed a hierarchical visual cryptographic method which doesn't suffer from any pixel expansion and found similar contrast as the original image. It uses the concept of full binary tree for generating share in (m, m) VCS up to n-1th (started from zero) level of its height where only left child in left sub-tree and right child in right sub-tree are further divided. A small size binary image of factor size of one of leftmost share in left sub-tree is used to generate key by doing XOR operation with this share and resultant share works as a key in this process.2013 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC); 12/2013
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ABSTRACT: Visual cryptography schemes (VCS) generate random and meaningless shares to share and to protect secret images. Conventional VCSs suffer from a transmission risk problem because the noise-like shares will raise the suspicion of attackers and the attackers might intercept the transmission. Previous research has involved hiding shared content in halftone shares to reduce these risks, but this method exacerbates the pixel expansion problem and the visual quality degradation problem for recovered images. In this study, a binocular VCS, called the (2, n)-BVCS, and an encryption algorithm are proposed to hide the shared pixels in the Single Image Random Dot Stereograms (SIRDS). Because the SIRDSs have the same 2-D appearance as the conventional shares of a VCS, this study tries to use SIRDSs as cover images of the shares of VCSs to reduce the transmission risk of the shares. The encryption algorithm alters the random dots in the SIRDSs according to the construction rule of the (2, n)-BVCS to produce non-pixel-expansion shares of the BVCS. Altering the dots in a SIRDS will degrade the visual quality of the reconstructed 3-D objects. Hence, we propose an optimization model that is based on the visual quality requirement of SIRDSs to develop construction rules for a (2, n)-BVCS that maximize the contrast of the recovered image in the BVCS.IEEE Transactions on Image Processing 08/2014; DOI:10.1109/TIP.2014.2346026 · 3.11 Impact Factor
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ABSTRACT: In a conventional threshold $k$ out of $n$ visual cryptographic scheme (($k,n$)-VCS, for short), one secret image $P$ can be encoded into $n$ seemingly random transparencies (called shares) such that the superimposed result of any group of $k$ or more transparencies can reveal $P$ to our eyes, while that of less than $k$ ones cannot. To ease the management and identification, the shares may look meaningful, instead of seemingly random, pictures. Given secret image $P$ shared by $n$ participants and cover image $C$, we study ( $k, n$)-VCS with meaningful shares (denoted as ($k, n$)-VCS-MS) in this letter where the $n$ shares could be recognized as the meaningful cover $C$ and their superimpositions follow the threshold requirements of ($k, n$)-VCS. We present a formal definition to ( $k, n$)-VCS-MS and develop an efficient construction by way of integer line- r programming. Experimental results demonstrate the effectiveness of our construction.IEEE Signal Processing Letters 12/2014; 21(12):1521-1525. DOI:10.1109/LSP.2014.2344093 · 1.64 Impact Factor